Encoding device employing a cathode ray tube



Dec. 10, 1963 w. VEITH ETAL 3,114,073

ENCODING DEVICE EMPLOYING A CATHODE RAY TUBE Filed April 9, 1962 I5 Sheets-Sheet 1 Fig.1

'A $2 n l "V4 4% Dec. 10, 1963 w. VEITH ETAL 3,114,073

ENCODING DEVICE EMPLOYING A CATHODE RAY TUBE Filed April 9, 1962 s Sheets-Sheet 2 Fig.3

2 Fig.8

Dec. 10, 1963 w. VEITH ETAL ENCODING DEVICE EMPLOYING A CATHODE RAY TUBE 3 Sheets-Sheet 15 Filed April 9, 1962 2H 9mm United States Patent 3,114,073 ENCODING DEVICE EMPLOYING A CATHODE RAY TUBE Werner Veith, Munich, and Hinrich Heynisch, Grafelfing, near Munich, Germany, assignors to Siemens & Halske Aktiengesellschaft Berlin and Munich, a corporation of Germany Filed Apr. 9, 1962, Ser. No. 186,133 Claims priority, application Germany Apr. 12, 1961 9 Claims. (Cl. SIS-85) The invention disclosed herein is concerned with an encoding device for converting a continuous signal function of desired configuration into a corresponding current impulse sequence which is, for example, adapted to a binary system.

Among encoding devices of this kind is a type comprising an electron beam tube (encoding tube) comprising a screen which is in suitable manner perforated (raster mask) and scanned by an electron beam, the beam sweeping over or hitting one of the stages (raster lines) disposed by the vertical subdivision one below the other, depending upon the deflection thereof, for example, in vertical direction, effected by the signal which is to be encoded. Depending upon which binary powers are occupied in such a horizontally, that is, line-wise disposed stage, therefore representing jointly the stage value or numerical value, respectively, there are provided corresponding cutouts (holes) through which the electron beam reaches the collector which is disposed in back thereof. Only predetermined momentary values of the signal curve, with mutually constant spacing, appearing successively in similar intervals, are thereby used as control voltages for the deflection of the electron beam. Accordingly, the electron beam is during such a time interval, the socalled encoding time, not altered in its vertical deflection, receiv ing only at the beginning of the next following time interval abruptly another deflection corresponding to the momentarily prevailing value of the signal curve. Assuming that the electron beam is a flat beam, so that it always impacts a stage (raster line) along its entire length, and further assuming that a number of separate collectors, corresponding to the place number of the code, are provided in back of the screen, there will be simultaneously produced a group of impulses in the manner of a local resolution. However, if the electron beam sweeps continuously over the respective stage (raster line) in the manner of line writing, the corresponding group of impulses will successively appear upon a common collector disposed in back thereof, that is, there will be a resolution in point of time. Since the impulses are ultimately used successively as to time, they must be in the case of local resolution converted into a time sequence, which can however be eiiected in simple manner by means of delay members.

Tubes operating with locally resolved impulse groups are, as compared with tubes operating with resolution as to time, structurally considerably simpler; for example, the continuous scanning along the individual raster lines, by means of a rotary field, is eliminated.

Accordingly, the object of the invention is to provide an encoding device employing an encodin tube operating with local resolution, for converting a signal function into an impulse sequence which, among others, occasions imaging errors as slight as possible, which has a low input capacitance, and which requires only low operating volt- In accordance with the invention, this object is realized in connection with the previously described encoding device employing a cathode ray tube, especially for pulse code modulation, by the provision, as a deflection means, of a transverse field serving also for the focusing, with the use of a deflection capacitor, for example, a plate capacitor, one plate of which is provided with a longitudinal input slot formed therein and a perforated screen with raster lines extending parallel thereto, the fiat electron beam being gunned into the capacitor space through the entry slot with respect to this capacitor plate, with an angle of inclination of 45, the socalled focusing angle, and being deflected approximately along a parabolic path and focused upon one of the raster lines by the action of an auxiliary opposing field corresponding to a signal value, which is superimposed on an opposing field corresponding to a bias.

The invention is based upon the following thoughts: Upon gunning into a plate capacitor, through a slot formed in one plate, an electron beam, for example, a flat beam, at a small angle of incidence, less than 45 with respect to the corresponding plate, and placing on the plates a voltage which produces an opposing electric field, there will be obtained a parabola-like trajectory such that a line focusing of the beam, corresponding to the shape of the entry slot, will result upon the capacitor plate, at the place of impact of the electrons. The beam is accordingly upon traversing the capacitor space, continually deflected and focused. Upon varying the gunning velocity of the electrons or the magnitude of the opposing field produced by the voltage connected, the focusing will be completely preserved-only the impact point will be varied. It is in this manner depending upon the ratio of opposing voltage (deflection voltage) and gunning voltage, possible to obtain for the flat beam different gunning distances. This however presents, in the case of an encoding tube, the possibility of always hitting with the electron beam, upon a screen (mask) arranged, for example, in parallel with the plane of the capacitor plate or upon the capacitor plate itself, a certain one of the many raster lines. Owing to the perforation of the screen, the electron beam simultaneously reaches, through the respective cutouts (holes), collectors disposed in back thereof, the number of collectors corresponding to the place number of the code that is being used. Eight separate collectors are required upon using, for example, an eight-place code. Upon connecting the collectors over corresponding delay members with a common line, the impulses appearing simultaneously on the individual collectors, will appear on such line in succession as to time. Upon successively altering, for example, in accordance with a bias voltage, the opposing voltage existing on the plate capacitor, or the voltage which determines the velocity at which the electrons are gunned into the capacitor, with briefly held voltage values, by superposing the bias voltage, such as are obtained, for examples, at the scanning of a signal function, there will appear in the encoding tube successive impulse groups which may also be resolved as to time, in the manner described, thus obtaining a pulse code which may be utilized for the modulation of a transmitter.

Only the central region of the flat beam will be utilized, considering the fact that imaging errors would result from the use of the lateral region and also due to space charge effects. It will also be necessary to provide for a relatively great lateral extent of the opposing field plate capacitor so as to avoid disturbance of the deflection operation by the marginal distortion of the opposing field.

In order to avoid the described drawbacks, the invention proposes in accordance with another object and feature thereof, to shape the capacitor in the form of a cylindrical capacitor, and to gun the electrons at the focusing angle given by such arrangement with respect to the axis of the cylindrical capacitor. The gunning angle for optimum focusing condition depends in connection with a cylindrical capacitor primarily upon the ratio of the radii r,,/ r The focusing angle is 45, the greater r,.,/ r,. In the case of an extreme ratio, for example, r /r 10, the focusing angle will become undesirably dependent upon the gunning distance.

45 for the focusing angle will again be obtained at the border transition to the plate capacitor. There will then be obtained, under the influence of the opposing field, a focusing and deflection of the beam along trajectories extending in the manner of onion peeling. The raster lines extend correspondingly respectively in the form of closed circular rings or very narrow closed cylinder envelopes.

Further details of the invention will appear from the description which is rendered below with reference to the accompanying purely schematic drawings.

FIG. 1 shows in schematic manner the operation of a plate capacitor as a deflection system for the encoding tube of an encoding device;

FIG. 2 indicates the structure and function of such a device operating with an encoding tube comprising a cylindrical capacitor;

FIGS. 3 to 8 represent Variants of a deflection system of an encoding tube, constructed in the form of 21 capacitor haying coaxially extending tubular inner and outer electrodes; and

FIG. 9 shows the principal circuitry of the encoding device to be described herein.

Like parts are indicated'in the drawings by like reference numerals.

In FIG. 1, numerals 1 and 2 indicate the two capacitor plates of a plane deflection system for an encoding tube. A flat beam 5 from an electron beam producing system (not shown) is by the action of an auxiliary opposing field, produced between the plates 1 and 2, deflected through the slot 3 along an approximately parabolic. path or trajectory, to the raster '4 (screen) provided upon the plate 1 and extending in parallel to and spaced from the slot 3, so that it always hits a raster line throughout its entire length or extent. The angle of incidence with respect to the capacitor plate corresponds to the focusing angle of 45. Numeral 8 indicates the spreading angle of a few degrees which delimits the flat electron beam about the focusing angle. Eight separate wires 6 corresponding to an eight place code, forming collectors, are provided underneath the capacitor plate 1 within the region of the perforated screen. Accordingly, upon impact of the flat electron beam, electrons will reach the respective collectors only at the places which are delimited by holes.

FIG. 2 shows in purely schematic manner, omitting the discharge vessel, the structure of an encoding tube comprising a deflection system made in the iorm of a cylindrical capacitor. Within the inner cylinder 1 of the capacitor, approximately at one end thereof, is disposed the beam generating system comprising the cathode 9 and the Wehnelt cylinder 10. Spaced from the emission plane of the cathode is an annular slot 3 formed in the wall of the inner cylinder 1, as an entry opening for the electron beam extending [from the cathode in the form of a cone and already focused by the Wehnelt cylinder, such beam being, by the action of the applied signal voltage, with maintenance of the focusing angle in the deflection space, by the opposing held and superposed field, deflected approximately in thegeneral shape of onion peeling and the-reby'focused as a narrow cylinder envelope, upon the perforated screen 4 which extends toward the other end of the inner cylinder. This socalled illumination of the slot aperture or diaphragm 3, by the bending of the electrons emitted from the emis- 4 sion plane of the cathode frontally to the cylinder, in the manner of an open cone, is among others obtained by the action of a deflection electrode 11, formed, for example, as a cone geneatrix, which is disposed in the region of the slot so that it approximately occupies the crosssectional area of the inner cylinder, its apex being directed to the emission plane centrally thereof. Depending upon the potential of this electrode, the electrons will be focused upon the slot or, for purposes of spotting the beam, deflected upon the cylinder wall. The slot is by this device pictured upon the perforated screen 4 in approximately parabolic curve manner, as an electron source, in a ratio of 1:1. The perforation of the screen forms closed raster lines arranged in parallel relation to the entry slot, suchlines representing the respective stage values. In back of this perforated screen, that is, within the inner cylinder, are disposed eight wires 6 corresponding to the eight place code, such wires being spaced from the wall and symmetrically distributed, and forming separate collectors. Electrons will reach the respective wires or collectors only throughcutouts (holes) in the screen. The individual collectors are mutually shielded by individual radially extending metal sheets 12 which are centrally combined to form a common structure, as is indicated in perspective representation in the cutout portion of FIG. 2. The subdivision of the screen with respect to raster lines is very fine, considering the fact that an eight place code embraces 256; numbers (values). The subdivision, that is, the vertical subdivision in raster lines is, as ascertained by exact calculation, not strictly linear.

The cylindrical capacitor of such an encoding tube as well as the kind of electron gunning used in connection therewith, can be modified in many ways. Thus, it is possible, by particular configuration of the electrodes, to obtain, for example, a stretching or extension of the raster division and therewith an enlargement of the raster mask, calling for requirements which are not as strict insofar as the electron optics and the deflection operations are concerned. Moreover, different functional relationships between the control voltage (deflection voltage) and the point of impact of the electron beam will be obtained depending upon the modified form and arrangement of the cylindrical capacitor. It is, for example, possible to extend the raster at places at which the imaging errors of the beam are greatest. It is likewise possible'to achieve a linearization'of the relations existing between the control voltage and the deflection.

FIGS. 3 to 8 show in schematic manner a few of the possible embodiments. V

In the embodiment shown in FIG. 3, the outer deflection electrode 2. of the socalled cylinder capacitor is formed as a truncated cone envelope the flat electron beam entering at the wide end thereof.

In FIG..4, the deflection system is constructed similarly, but the electron entry is effected at the narrow part of the outer electrode. This embodiment permits in particularly advantageous manner .an elongation of the screen and therewith widening of the raster lines.

In FIG. 5, the outer deflection electrode 2is formed as a truncated cone envelope, as in FIG. 3. However, the electron beam producing system is not disposed within the cylindrical inner electrode, as illustrated in 'FIG. 2, but outside of the deflection system proper. The electrons emitted from the centrally arranged generating system are focused in the manner of a cylinder envelope and enter into or illuminate the annular slot of a circular disk 13, acting as an acceleration anode, which is disposed in parallel to but ahead of the common frontal plane of thetwo deflection electrodes.

FIG. 6 shows a further variant of this arrangement, differing from that indicated in FIG. 5, merely in utilizing an outer deflection electrode 2 which is curved to form a rotation plane instead of a truncated cone. Particular deflection characteristics may beobtained, if desired, by varying the curvature. Y

FIG. 7 indicates a deflection system made, for example, in the form of a cylindrical capacitor, wherein one continuous electrode, that is, the outer deflection electrode without an entry slot and perforated screen, is subdivided into two parts. Both parts 2 and 2' are in the illustrated example approximately of equal length. It is, however, possible and particularly advantageous to make the part of the electrode, which is near to the cathode, considerably shorter. This measure is analogously applicable in the case of plane systems and likewise in systems having a conically shaped or curved outer electrode.

In the embodiment shown in FIG. 8, the part 2' of the subdivided electrode which is disposed near the cathode, is in particular advantageous manner formed, for example, as a frustum of a cone, conforming approximated to the initial path of the flat electron beam, such part 2' being surrounded by the second elongated part 2 which is cylindrically shaped. The short partial electrode 2 is thus positoned completely within the long cylinder and is additionally screened by the latter.

The particular advantage of the above described measure resides in that it is possible to separate the control operation, which effects the deflection of the electron beam, from the focusing and deflection operation which is necessarily eflected in an elongated deflection system. It must be considered in this connection that the focusing and simultaneous deflection of the electron beam along a parabolic path, the socalled zero or initial path, corresponding approximately to the characteristic working point of an amplifier tube, is in practice effected by an opposing field produced by a constant bias voltage and by the simultaneously applied signal voltage which produces a superposed auxiliary opposing field, the latter deflecting the electron beam from its zeroor initial path for the purpose of impacting the respective raster lines. The previously described subdivision of the continuous or outer electrode, for example, respectively into a long and a short partial electrode, with the object of conducting the control voltage, that is, the momentary signal value, additionally solely to the short partial electrode, makes it possible to considerably reduce the capacitance of the input system and consequently to carry out encoding to approximately the nano-second range sec.). Moreover, the last described subdivision of an electrode of the deflection system, is adapted to obtain, in simple manner, for example in the case of a cylindrical deflection capacitor, by formation of the short partial electrode as a delay line with a delay which is effective in asimuthal direction, an impulse sequence which is resolved as to time, requiring, however, changing of the electron beam as to its shape and imparting thereto a cycling motion by the use of a rotary field.

FIG. 9 represents in principal, the circuit of an encoding device comprising an encoding tube, the discharge vessel being for the sake of simplicity omitted. The outer deflection cylinder 2 which is disposed opposite the grounded inner cylinder 1, is on negative potential from the current source 14. The signal input is disposed between the grounded reference point and the battery 14, being represented in the form of a signal transmitter from which the deflection system receives a stepped voltage sequence, matched to a signal function to be encoded, for producing a superposed opposing field for control purposes. Within the inner cylinder 1 are disposed the cathode 9, the Wehnelt cylinder 10 and the deflection electrode 11, such parts being with respect to the grounded reference point on a negative potential from the voltage source 15. A scanning voltage transmitter T is inserted in the line extending from the voltage source to the deflection electrode 11, the rectangular voltage impulses from such transmitter controlling the illumination of the entry slot or gap 3. Within the inner electrode, at the other end thereof, are provided the individual collectors 6, each collector being isolated by capacitances C, and receives from the voltage source 16 a potential which is higher with respect to the reference potential. The impulses appearing at the respective collectors are, prior to the extension thereof over a common line, delayed by suitable delay members (not shown).

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim:

1. An encoding device having a cathode ray tube operating as an encoding tube, said tube including a beam deflection capacitor comprising coaxially extending radially spaced apart tubular inner and outer electrodes forming an axially extending annular capacitor space, an electron beam generating system, for producing a flat beam disposed outside of said capacitor space, a beam entry slot formed near the end of the inner electrode which faces the beam generating system, said inner electrode having perforations formed therein, axially spaced from said slot, corresponding to stages of an encoding system, collector means disposed in back of said perforations, whereby said flat electron beam is at a fixed acute focusing angle gunned through said slot into the capacitor space, the electrons of said beam moving along approximately parabolic paths longitudinally of said capacitor space, and means for placing a signal voltage on the deflection capacitor, operative to focus the beam for impacting collector means of the respective stages of the encoding system disposed in back of the perforations formed in said inner electrode, thereby producing groups of impulses according to the spatial disposition of said perforations.

2. An encoding device according to claim 1, wherein said entry slot is formed in said inner electrode, comprising, disposed within said inner electrode, approximately in the vicinity of said entry slot, a deflection electrode formed in the configuration of the frustum of a cone with the apex thereof facing in the direction of the beam generating system.

3. An encoding device according to claim 1, wherein at least part of said beam generating system is disposed within said inner electrode, and wherein said entry slot is formed in said inner electrode, comprising, disposed within said inner electrode, approximately in the vicinity of said entry slot, 2. deflection electrode formed in the configuration of the frustum of a cone with the apex thereof facing in the direction of the beam generating system.

4. An encoding device according to claim 1, wherein wires disposed in back of the respective perforations constitute said collector means, comprising radially extending metallic members for shielding the individual collector wires.

5. An encoding device according to claim 1, wherein said outer electrode is subdivided to form two parts, the line of subdivision extending in parallel with the line along which is disposed said beam entry slot, the part of said subdivided outer electrode which faces the beam generating system being connected to the signal voltage and servmg solely for the angular deflection of the beam into the capacitor space, and the other part of such electrode being connected with a constant bias voltage which efiects the deflection of the beam and focusing thereof with respect to the perforations formed in the inner electrode.

6. An encoding device according to claim 1, wherein said inner electrode is of cylindrical configuration, comprising an outer conical electrode, the narrow end of said outer electrode facing the beam generating system.

7. An encoding device according to claim 1, wherein said inner electrode is of cylindrical configuration, comprising an outer electrode of longitudinally tapering configuration, the beam producing system being disposed outside of said deflection capacitor as seen in axial direction thereof, and a circular plate forming an entry diaphragm extending in parallel with and spaced from the common frontal plane of the two deflection electrodes.

8. An encoding device according to claim 5, wherein the part of the subdivided electrode which faces the electron beam generating system is relatively short and surrounded by the other longer part.

9. An encoding device according to claim 8, wherein said relatively short part is of a configuration conforming substantially to the frustum of a cone, said other longer part being of cylindrical configuration.

References Cited in the file of this patent UNITED STATES PATENTS Clark Oct. 9, 1951 Giacoletto July 15, 1952 Goodall Oct. 28, 1952 Lafierty Apr. 10, 1956 

1. AN ENCODING DEVICE HAVING A CATHODE RAY TUBE OPERATING AS AN ENCODING TUBE, SAID TUBE INCLUDING A BEAM DEFLECTION CAPACITOR COMPRISING COAXIALLY EXTENDING RADIALLY SPACED APART TUBULAR INNER AND OUTER ELECTRODES FORMING AN AXIALLY EXTENDING ANNULAR CAPACITOR SPACE, AN ELECTRON BEAM GENERATING SYSTEM, FOR PRODUCING A FLAT BEAM DISPOSED OUTSIDE OF SAID CAPACITOR SPACE, A BEAM ENTRY SLOT FORMED NEAR THE END OF THE INNER ELECTRODE WHICH FACES THE BEAM GENERATING SYSTEM, SAID INNER ELECTRODE HAVING PERFORATIONS FORMED THEREIN, AXIALLY SPACED FROM SAID SLOT, CORRESPONDING TO STAGES OF AN ENCODING SYSTEM, COLLECTOR MEANS DISPOSED IN BACK OF SAID PERFORATIONS, WHEREBY SAID FLAT ELECTRON BEAM IS AT A FIXED ACUTE FOCUSING ANGLE GUNNED THROUGH SAID SLOT INTO THE CAPACITOR SPACE, THE ELECTRONS OF SAID BEAM MOVING ALONG APPROXIMATELY PARABOLIC PATHS LONGITUDINALLY OF SAID CAPACITOR SPACE, AND MEANS FOR PLACING A SIGNAL VOLTAGE ON THE DEFLECTION CAPACITOR, OPERATIVE TO FOCUS THE BEAM FOR IMPACTING COLLECTOR MEANS OF THE RESPECTIVE STAGES OF THE ENCODING SYSTEM DISPOSED IN BACK OF THE PERFORATIONS FORMED IN SAID INNER ELECTRODE, THEREBY PRODUCING GROUPS OF IMPULSES ACCORDING TO THE SPATIAL DISPOSITION OF SAID PERFORATIONS. 